Understanding Research Design Can have confusing terms Research Methodology

The entire process from question to analysis Research Design

Clearly defined structures within which the study is implemented

Is a large blueprint, but must be tailored to the study and then mapped out in detail

Quantitative Design Concerns

Primary purpose (check question) Is there a treatment (intervention) Will the treatment be controlled Is there a control group (untreated) Is there a pre or post test (or both) Is the sample a random sample Will the sample be a single group or

divided into several groups

Quantitative Design Concerns-2

How many groups will there be What is the size of each group Will groups be randomly assigned Will there be repeated measurements Will the data be collected cross-sectionally

or over time Have extraneous variables been identified

and controlled for What strategies are being used for

comparison of variables or groups

Study Validity Def: It is an examination of the

approximation of truth or falsity of the propositions Statistical Validity Internal Validity Construct Validity External Validity

(Cook and Campbell, 1979)

Statistical Validity Errors Violate assumptions about the data

Nominal, ordinal, interval, ratio data Type I and Type II errors Need for Power Analysis

Predicts the necessary N value Inappropriate use of certain statistics

for the various types of data Random irrelevancies in setting Random heterogeneity of respondents

Numbers and Use of Numbers Nominal (qualitative)

A Named category given a number for convenience, e.g. males are 1 and females are 2

Ordinal (qualitative) A scale that is subjective but shows a direction, e.g.

pain scale, cancer staging Interval (quantitative)

Numbers where the interval between them is meaningful, e. g. a temperature

Ratio (quantitative) Numbers where the ratio to each other has meaning,

e. g. a pulse, heart rate.

Statistical Conclusion ValidityType I and Type II Errors

Accept the Null Hypothesis Reject the Null Hypothesis Reality is: Type I ErrorNo Wanted There is no differencedifference caused by fishing

Reality is: Type II Error, there is There is a difference often caused WantedDifference by a low N value

Internal Validity Definition:

*It is the extent to which the effects detected in the study are a true reflection of reality rather than the result of extraneous variables;

* The independent variable did have an impact on the dependent variable

Threats to Internal Validity History: Natural events over time impacting

the subjects Maturation: A person’s growth in any area

impacting his/her response Testing effect caused by subjects

remembering previous testing Instrument reliability of treatment Selection process (randomized) Mortality threat Interaction with subjects No equalization of treatment

External Validity Definition:

To provide development of the design that allows it to be generalized beyond the sample used in the study.

Most serious threat is that it can only be said of the group being studied

Threats to External Validity Small N No randomization when it is needed Special probability sampling

Simple Stratified Clustered Systematic

Single vs. replicated

Quantitative Designs Experimental (Solomon) Quasi-experimental Descriptive Case Study Correlational